A thin film transistor is a thin film semiconductor switching device, which is widely used in the fields of display technology (for example, liquid crystal display technology and organic light emitting diode display technology), integrated circuit technology and so on. Regardless of a liquid crystal display device (LCD) and an organic light emitting diode (OLED) display device, thin film transistors (TFTs) are arranged as the control switches.
Usually, preparing of a thin film transistor includes the following steps: forming a gate electrode through a patterning process, and then forming a gate insulating layer film and an active layer film. An active layer is formed through a patterning process; an etching barrier layer is formed through a patterning process on the corresponding position, for forming a channel area, of the active layer. A source-drain electrode film is formed and then source and drain electrodes are formed through a patterning process. The impact of a source-drain (SD) etching solution on the active layer channel area can be prevented by the formed etching barrier layer. However, an etching barrier layer covering the active layer will inevitably bring about complexity and difficulty to the preparation process. In addition, a mask process is added, and the step and cost are also increased.